IEC 61000-4-11 — voltage dips, short interruptions, and voltage variations immunity testing — is one of the most commonly cited but loosely specified requirements in AC power test procurement. Getting the details wrong doesn't just under-spec the system — it can produce non-compliant results that pass equipment a properly configured system would have failed.

What IEC 61000-4-11 Actually Requires

The standard defines test conditions for voltage dips, short interruptions, and voltage variations, each specifying a target voltage level and duration. Critically, these transitions need to happen at a specific, controlled point in the AC waveform, and the transition itself needs to be fast enough to accurately represent a real grid event.

Voltage Slew Rate — The Specification Most Often Under-Speced

If slew rate is too slow, the dip the DUT actually experiences is shallower and slower than the standard requires. The CORTEX AC series specifies a voltage slew rate above 3V/μs with a 100μs response time — fast enough that the transition itself doesn't become the limiting factor.

Phase Angle Control — Required for Repeatable, Standard-Compliant Testing

Phase angle control with fine resolution. The CORTEX AC series provides 0–359.9° phase angle control at 0.1° resolution, with single-phase and three-phase channels independently controllable.

Independent three-phase control, not just balanced three-phase output, is required for asymmetric dips across phases in some test conditions.

Built-In Waveform Libraries — Why They Matter for Compliance

Manually programming dip depth, duration, and phase angle for every test point is time-consuming and error-prone. The CORTEX AC series ships with built-in support for IEC 61000-4-11, 4-13, 4-14, 4-17, 4-27, 4-28, and 4-29, plus China's T/CPSS1007-2020 grid code — reducing programming error and covering the full standard family most real test programs actually need.

Regenerative vs Non-Regenerative — Does 61000-4-11 Specifically Need It?

IEC 61000-4-11 testing itself doesn't inherently require a regenerative supply. However, regenerative capability becomes relevant for grid-connected inverter/ESS testing and anti-islanding/LVRT testing run alongside it, where the DUT actively generates power the simulator needs to absorb. The CORTEX AC series combines 4-quadrant regenerative operation with 61000-4-11 dip capability in the same unit, feeding absorbed energy back at over 91% efficiency.

Practical Specification Checklist

1. Confirm voltage slew rate and response time against the standard's required transition speed.
2. Confirm phase angle control resolution and independence match the test plan.
3. Check for a built-in IEC 61000-4-11 waveform library.
4. Identify whether the broader program needs 61000-4-13/14/17/27/28/29 or IEEE 1547 alongside it.
5. Determine whether the DUT is itself a power source requiring regenerative capability for adjacent LVRT/anti-islanding testing.